A Novel Scaling Theory for Fully Depleted Omega-Gate MOSFETs Included With Equivalent Number of Gates

Abstract

A novel scaling theory for fully depleted omega-gate (ΩG) MOSFETs, including rectangular-shaped ΩG (RΩG) and cylindrical-shaped ΩG (CΩG) MOSFETs, is presented. The natural length for the ΩG MOSFET is obtained by solving the equation of equivalent number of gates (ENG), where the ENG of the ΩG device working in the x-y-z space can be the sum of the ENGs for both the double-gate (DG) and single-gate transistors working in the y-z and x-z planes based on the perimeter-weighted-sum method. Numerical device simulation data for drain-induced-barrier-lowered effects (DIBL) were compared with the model to validate the theory. Among the RΩG devices with the same perimeters, one with a square cross section and a large oxide-to-gate underlap coverage factor (OUCF) will show the worst immunity to the DIBL due to the largest natural length. For equivalent short-channel controlling capability, the RΩG MOSFET with the OUCF=0.7 illustrates an improvement of up to 25% in the minimum effective channel length Lmin when compared with the DG MOSFET.